The candidate?s long-term career goals are to become an independently funded Principal Investigator in an academic, industrial, or government setting. The candidates research career development plan includes the analysis of G-protein coupled receptors (GPCRs) with respect to cell signaling and physiological function, such that novel therapeutics can be developed to combat disease. The primary focus of the current proposal is to analyze the regulation of G-protein signaling mediated by the receptor for parathyroid hormone (PTH) and parathyroid hormone related protein (PTHrP). Specifically, the research goal is to determine the functional significance of the interaction between the parathyroid hormone receptor (PTH1R) and the Na+/H+ exchanger regulatory factor 2 (NHERF2). The PDZ domains located within NHERF2 mediate the basic PTHR interaction both in vitro and within mammalian cells. When co-expressed in PS120 fibroblasts, NHERF2 effectively shifts the PTH1R signaling pathway from adenylyl cyclase to phospholipase C. The presence of NHERF2, therefore, will profoundly influence the tissue-specific effects of parathyroid hormone. The purpose of Specific Aim 1 is to elucidate the mechanisms by which NHERF2 functions as a "molecular switch" with respect to PTH1R cell signaling. Phospholipase Cbeta1 and beta2 interact with NHERF proteins. Therefore, the ability of NHERF2 to facilitate the formation of a complex consisting of PTH1R and phospholipase C will be examined. Specific aim 2 will focus on demonstrating the NHERF2 mediated effect on PTH1R signaling in the context of a polarized cell model. PTH1R expressed on apical membrane of renal epithelia fail to signal via adenylyl cyclase, but demonstrate signaling via phospholipase C. Conversely, PTH1R located on basolateral surfaces preferentially signal via adenylyl cyclase. The hypothesis is that apically localized NHERF2 instills the characteristic signaling patterns of the PTH1R located on apical membranes in renal epithelia. The goal of Specific Aim 3 is to identify the amino acids that direct the specificity of the PTH1R-NHERF2 interaction.